People close to Mr. Alexander say they have no idea whether he will vote to allow witnesses — and that he may not know yet himself. Should he do so, he would be a “pariah” in the state, said one conservative activist in Tennessee, who requested anonymity to speak candidly about a sitting senator…

“Lamar is not looking for a one-time event to have what I call the shocking headline,” said Tom Griscom, a close friend of Mr. Alexander and former press secretary to Mr. Baker. “You’ve got a template of who he is over a career — that doesn’t change. He’s not looking to write a post-note at the back end of it.”…

John Geer, a political scientist at Vanderbilt University and co-director of the Vanderbilt Poll, said his surveys show a “strong majority” of Tennesseans believe Mr. Trump did “something wrong,” and while Mr. Alexander is under pressure from conservatives, “the Baker wing” of the Republican Party would stick with him if he voted for witnesses.

“He’s not voting for impeachment; he’s made that very clear,” Professor Geer said. “He’s voting to learn more, which is frankly something pretty easy to defend.”